The problem is really what do you do with a lot of people who need to do anything and probably don't need to exist? They tend to multiply quite rapidly as well as there is nothing else to do.
In a society that demands employment, 50% unemployment is a death-sentence. That's half your population draining the subsidies dry and raising taxes on the working half. Suddenly both sides are angry. Prisons become overburdened, people dead in the streets, Governments overthrown, CEO assassinations, etc.
Sure, in a fantasy land where things don't cost money and land isn't 'owned', 50% unemployment could be ok. Unfortunately that's not us yet.
Society is polarised by automation. The gap widens every day.
I've destroyed hundreds if not thousands of manual work positions over the years by making software that replaces them. I've now got to support the uenmploymed with my tax contribution. Welcome to the flawed turd-bag that capitalism is.